Automatic motor control.



W. S. MITCHELL.

AUTOMATIC MOTOR CONTROL. APYPLIGATION FILED APR.17,1912.

1,106,469, Patented Aug.11,1914.

W. S. MITCHELL.

AUTOMATIC MOTOR CONTROL.

APPLICATION FILED APR. 17. 1912.

1,106,469. Patented Aug. 11, 1914.

3 SHEETS-SHEET 2.

fa Zine 4 5,3

- control switch suitable for the accelerating closing the control switch of the motor,

my invention, for a direct current, shunt where the control switch is automatically closed by low pressure n an air reservoir and opened at high pressure; or wherever.

STATES PATENT OFFICE.

WILLIAM S. MITCHELL, OF SOMERVILLE, MAS SACHUSETTSJASSIGNOR 0F ONE-THIRD TO JOSEPH W. SMITH, 0F PATERSON, NEW JERSEY.

AUTOMATIC MOTOR CONTROL.

Specification of Letters Patent.

Patented Aug. 11, 1914.

Application filed April 17, 1912. Serial No. 691,409.

To all whom it may concern:

Be it knownthat I, WILLIAM S. MrrcHELL, a citizen of the United States, and resident of Somerville, in the county of Middlesex and State of Massachusetts, have invented new and useful Improvements in Automatic Motor Control, of which the following isa specification. I

This invention relates to automatic motor controls, and its object is to provide novel and improved systems of acceleration and deceleration of motors, as hereinafter more fully described and pointed. out in g the claims.

In the drawings hereto annexed which illustrate diagrammatically certain adaptations of the 'invention,-'Figure 1 illustrates an automatic accelerating device containing wound motor, having a single running point or speed; Fig. 2 illustrates an automatic accelerating device containing my invention for a compound wound, reversible motor having three running points; Fig. 3 illustrates an automatic accelerating and a decelerating device, containing my invention, for a compound wound motor; Fig. 4 shows in 'side elevation a magnetically operated and decelerating system of Fig. 3; Fig. 5 is a diagrammatic view illustrating the arrangement of the contacts and wiring of said switch; and Fig. 6 isa diagrammatic illustration of the wiring of such switch.

The device illustrated in Fig. 1 is applicable to situations where it is desired upon either automatically or by hand, tostart the motor, permit it to accelerate to full speed, and to stop it by opening the control switch. This arrangement is adaptable to such purposes as the starting of a motor on a pump. by a float switch; or on an air compressorv it is desired merely to start and stop a motor, which runs in one direction, by simply closing and opening the control switch. 7.

Referring to Fig. 1 of the drawings, A represents the armature of the motor, and B the shunt field. Current is supplied from the main line conductors l and 2, which are connected by switch 3 with conductors 4 and 5, respectively. By closing the main control switch S, magnet coils G and D will be energized, the circuit thereof being closed from conductor 4 through conductors 6 and 7 to conductor 5.. The energizing of magnets C and D closes'switches E and F and completes the circuit through the armature A and its starting or controlling resistance, G, H, I,

and through the shunt field B. When the motor starts, all the sections G, H, I, of the starting resistance will be in the armature circuit. As the motor speeds up it will generate counter velectromotive I force through the control circuit, which is connected at its .V in a circuit which whenclosed cuts out or short circuits the starting resistance G, H,-'I.

When the counter electromotive force generated through the control circuit is sufficient, owing to the difi'erence of potential between points 8 and 9, to energize the lifting or operating coil K and close the switch of electromagnet N, the armature circuit willbe closed through holding coil T, thereby cutting outsection G of the starting resistance, and sending'current through coil T in preference to the high resistance of section G of the startingresistance. As soon as the switch at N makes contact and coil T is energized,coil T will finish the work of lifting the magnet core, and will efiect and maintain a firm closure or the switch. At the same instant coil T will open the interlock W thereby breaking the control circuit through the operating coil K. As the motor further accelerates, and the counter electromotive force'becomes sufficient to energize operating coils L and M successively, the switches at O and P will close in the same manner, at the points in the acceleration of the motor predetermined by the extent of the controlv circuit resistance R in circuit with coils L and M. When coil L is ener ized the switch at 0 will be closed, sections and H of the starting. resistance will be out out,

and P,

and raising 'coii o win be strange already described with reference to coil T,

tersatsa d hold qfi m c s e o t e switch of magnet O, vand open the control circuit by opening interlock X. And s1milarly, when coil M is energized it' will close the switch at P, out out all the starting re' sistances, energize, holding coil .V and open interlock Y. Thus it will be," seenthat at full speed or running point, the holding coils.

T,'U and V are in series in the armature circuit, the operating 'orlifting' coils K, L', M, are allopen circuited, and the control cir cuit resistance R is also open circuitedj The motor'is stopped by opening main control switch S, whereupon the switches of magnets'N, O, P, will all resume theirnormal or open circuit positions (by gravity or .by

springs) interlocks W," and'Y w'ill also resume their normal or: closed positions, and

switches E and F will also open, all ready Eeleration'in either direction of a compound M i if ItjlSdBSlIQd to start the motor forward,

"thecontrol circuit is not inaction. By movfor another operation 'jas described, upon closingswitch S.

Referring now to 2, I have illustrated the invention applied to the automatic, ac-

wdund motor with a number of running polnts, or speeds. 'These running points are herein shown for the purpose of illustration. Assuming the-main line switch?) to be closed,

thecon'trol switch '8 is thrown to theright until contact is made with segment a. 7 rent then passes from conductor 4:, through conductor 10, switch arm S, contact seg-' ment a,conductor l1, electromagnet C, con-- ductor 12, electromagnet Dfand thence to conductor 5. Electromagnets C and D respectively close switches E and F and send the current fromt through armature JA,the

starting or controlling resistance G, H, l,

and'series fieldB to conductor '5, starting the .motor with all the startingresistanceand both theseri'es fieldlB and'the shunt field B in circuit. In the position thus far assumed ing theswitch'arm S farther toj the right until it. makescontact with segment 6 the control circuit is closed through conductor 10, which connects with the armature circuit' at one side of the armature, through oper'a'tingcoils K,"L andM, and resistance Rfwhioh connects with the armature circuit at theother side of the armature. Asoperating coils K,- L and M are successively en ergized they successively close'the switches "torspeed'has beenattained, the switch ai -m S may be swung into contact '-with segment [0, thereby closing the control circuit through o'pcrating-coil'g of electromagnet Q, closing the switch of that magnet, shortof electromagnets N, O and P, thereby energizing holding coils T, U and 'V and opening interlocks W, X and Y in succession, all as heretofore described. After the full mociiicuitingtheseries field B,energizing holding coil '72, and opening interlock Z. If at the start the" switch arm S is moved-atoms into contact with all. three segments, a, 6

undo, the control will automatically accelerate the-motor to full speed, the starting resistanceG, H, I, being cut out step by p, and finally the series fieldqiB 'ibin'gi .automaticallyput out. If it be desired to reverse the motor the switch arm is moved to the left making contact with segment f and completing the circuit from conductor 4:,

conductor '13, magnet G which closes ,switch E magnet D which'closesswitch F and thenceto conductor 5, thereby sending current through armature A in reverse' directionr In other respects the action of the device is the same as when the motor is being operated forward.

Fig. 3 illustrates an adaptation of my inmotor to any point, and the deceleration of the motor to any point,,the motor herein shown being adapted to run in one direction, By operating control switch S so as to close connection between contacts 14 and 15, and point29 of switch S and between contacts 16 and 17, a circuit willbe closed from conductor 4, through contacts 14 and 15, conductor 18, in which may be any desired number of stop push buttons 9, electromagnetfC and thence to conductor 5. Theenergizing of magnetC closes switch E thereby closing the circuit through ar mature A, starting or controlling'resi stance G'r, l-L'L-series field B, and shunt field B.

through conductor 10.,slwitch S, segment f, I

.vention to the automatic accelerationof the r If thefcontrol switch S is allowed to come to open. ositionas soonas ma et switch E is closed, themotor will continue to run at the speed of that point, with the entire starting resistance and the series field in circuit, themagnet coil C gettin its current to hold switch E closed, throng conductors Y 19 and 18, 19 being connected to the arma ture circuit at 20, andthence to conductor 4 through closed switch E. If the control switch S be kept closed until sufficient speed is attained to generate the necessary counter 'electromotive force, current will be passed from line 'to contact JUL-point 29, thence through the first' section of control circuit resistance R, operating coil K of electro- 1 magnet N, interlock W, conductor 21, coni,

tacts '16 and 17, and conductor 22, ,to the armature circuit 'at the opposite side of the armature, This will cause the switch of electromagnet 'N to close, cutting out section G of the starting or controlling resistance,

energizing holding coil Tof electromagnetI N, and opening interlock W to break the controlling circuit through coil 1K, 'inthe manner already described; It the control switch s is'still kept closed in'the same di rection. the operating coils L, M and g will act succession, closing the switches of electromagnets O, P and Q, energizing holding magnets U, V and h, and opening interlocks X, Y and Z, all in proper'successionat predetermined points as hereinbefore described. The acceleration of the motor may be stopped at any point by opening the control switch S", and the motor will continue to run at the speed of that point. To'lower the speed of the motor the control switch S is operated so as to make connection between contact 23 and point 29, and between contactsj24 and 25. It will be noted that when coiLT ofelectromagnet N opens interlock W, it closes interlock W. Similarly, coil U closes interlock X and opens interlock X coilV closes interlock Y and opens interlock Y3; and coil it closes interlock Z and opens interlock Z Assuming that the motor is running at full speed with all the switches of electromagnets N, O, P and Q.

closed, and the control switch 8 in deceleratingposition, thecontrol circuit is from 19,

c point 29 ofswitch S ,-contact 23, and connormal position.

said

through, and allowingthe switch of 'electro' magnet Q to open thereby again cutting series field B into circuit with its armature. The returnof the magnet core of electromagnet Q to normal position, will also close interlock Z, open interlock Z and close interlock Z. The current from conductor 26. will thereupon. pass-through interlock Z conductor 27, interlock Y (which is at this time closed) operating coil M, resistance R, and thence as before, energizing coil M in opposition tocoil V, causing the switch of magnet P to open, cutting in section I of the starting or controlling resistance, and restoring the interlocks Y, Y and Y to their originalor Interlock Y being new open and interlock Y closed, the. current from 26 passes through interlock Z conductor 27, interlock Y conductor 28, closed interlock X, coil L, resistance R and thence as before, opening the switch of electromagnet 0, and restoring the corresponding interlocks to normal position, as already described with respect to magnet P, and so on through all the electromagnets and their associated switches and interlocks until all the starting resistance is again ina circuit with the armature. Thus it will be s'een that a decelerating control circuit is provided, controlled by a switch, adapted to energize said coils successively inreverse order to that of their. accelerating action, and to the current through the holding coils of the several electromagnets, thereby permitting the magnet cores and switches of the several electromagnets successively to return to normal or open position; and that upon the return of each magnet tonormal position, the decelerating circuit through the operating coil of that magnet is opened, and the decelerating circuit through the operating coil of the next magnet in-order is closed and so on'through the whole set. It willalso be observed that when the apparatus is in nor- ,mal position, before starting, all the main switchesof'the electromagnets N, 0, etc., are open; the decelerating circuit is open at both ends; and that as each such switch closes during the accelerating action, it connects its operating-coil to the decelerating circuit, and as each-succeeding switch is closed it disconnects the preceding operating coil from the decelerating circuit. Also that when the decelerating circuit is closed through" the main control switch S the decelerating circuit is established through the operating coil of the last of the electromagnets N, O, etc.v which was operated.

In Figs. 4, 5 and 6 I have illustrated a form of magnetically operated control switch (S of-Fig. 3) for controlling the accelerating and the decelerating circuits. A

rocker bar 30 is pivoted at 31 on a suitable standardor support 32, and carries at one end contact pieces 33 which respectively are adapted to close connection between points 15,14 and 29, and between points 16 and 17 of the accelerating circuit. At the other end v of bar 30 are contact pieces 34 which respecjti-vely are adapted to close connection between points 24 and 25, and between points and 29, of the accelerating circuit. Two electromagnet coils 35 and 36 actuate the rocker bar 30, to which the magnet cores 37 and 38 are pivotally connected through plungers 39 and 40. Pivoted to the magnet frames are latches 41 and 42 which respectively engage notches in plungers 39 and 40. Latches 41 and 42 are secured to and actuated by magnet pieces 43 and 44, which are normally urged away from the ma et frames by springs 45 and 46, thereby yieldinglyholding latches 41 and 42 normally in 39 and 40. When one of the coils, for ex ample 36, is energized, latch 42 is withdrawn from its notch, permitting core 38 to draw bar 30 at that end downward, and to swing the other end of bar 30 u ward, until 15, 14 and 29, and contacts 16 and 17, by connections 47 and 48 (Fig. 5) thus establishing the accelerating circuit. Similarly, if magnet coil 35 is energized, latch 41 will be withdrawn and contact pieces 34 will close contacts 24 and25, and contacts 23 icing coils in opposition to locked position inthe notches of plungers' the contact pieces on that endc ose contacts and 29, by connections 49 and 50, thus establishing the decelerating circuit: When the coil 35 or 36, as thecase may be, is deenergized, spring .51 will restore the rocker bar to its nOrmaLZ-centralv position, and anythrow by or rebound, whichmight -en-. danger the accidental closing of the set of contacts at the opposite end'ofbar 30,'willbe prevented by the automatic engagemen t of both spring-pressed latches 41 and' tz when the bar 30 reaches its central position. The coils; and .36 are energized by suitable switches or push buttons, and are prefer'ably in circuit with the main lines 4 and 5. As illustrated in Fig. 6, a conductor 52, which is connected to line 4, leads to one end or each-of coils 35 and 86, through normally open switches onpushbuttons 53 and 54:. The other en of each magnet; coil is connect-ed through conductor 55, in whichthere may be a resistance, to line 5. Uponclosing either one of said ush buttons 53 or 54:, the

circuit is complete through the corresponding coil, 35 or 36, and control switch S is thereby operated, establishing the circuits as already described. L

I claim: a

1. In combination, a motor having an armature, a resistance in circuit with. the ar-. mature, and a controller comprising a series of switches adapted to cut out the resistance step. by step, each switch being controlled by an electromagnet, and each electromagnet having a switch operating coil, and a switch holding coihsaid operating coils being in shunt and said holdmgcoils being in series with the armature, the'operat-ing coils being energized successively as the motor speeds up, and said holding coils being brought successivel int-o series with 'the armature by the actlon of the operating coils, where-- upon the: shunt circuits of the respective operating coils are-automatically opened. 2; Incombination, amotor having an armature, a resistance in circuit with the armature, and a controller comprising a series of switches adapted to cut out the resistance step by step, each switch-being controlled by A anelectromagnet, and each electromagnet having a switch operating coil and a switch 7 holding coil, theoperating coils being energized successively as the motor speeds up to operate'said switches successively, and sa-1d holding coils being energized 'successlvely by the o eration of said operatingcolls and being a apted both to open the circu ts of the operating coils respectively, and to mainelectromagnet having a switc operating coil .and a switch holding coil and-acontrol-cirmeans coils respectively andv to maintain a firm closure of said switches, and said controlcircuit resistance being open circuited when the motor is running at full speed.

4. In combination, a motor having an armature, a resistance and a series field in circuit with the armature, and a controller comprising a series of switches adapted to cut out the resistance step by step and finally to cut out the series field, each switch being controlled by an electromagnet, and each felectromagnetphaving' a switch operating coil and a switch holding coil, the operating ;coils being energized successively as the motor speeds up to operate said switches successively, and said holdingicoils being 'energizedsuccessively,by the Operation of said operat ng coils to maintain a firm closure of said switches. I

5. In combination, a\ motor having an armature, a. resistance in circuit with the armature, and a controller comprising a series of switches adapted to cut the resistance. out or in step by step, each switch being controlled by an electromagnet, and each electromagnet having a switch operatingcoil and a-switch holding coil, the operating coils being energized successively with the acceleration of the motor to operate said switches successively, said holding coils being energized successively by the operation of said operating coils to maintaiua-firm closure of said switches, and means to'energize said operating coils successively in reverse order to that ofthe accelerating action, and in opposition to the current passing through the holding coils, thereby nullify- ,ing the magnetic flux through the holding (0118, and allowing said switches, to open successively to dccelerate' the speed of the motor. 7

6. In combination, amotor having an armature, a resistance in circuit with the armature, and a controller comprising a series of switches adapted to cut the resistances out or in step by step, each switch being controlled by an electromagnet and each electromagnet having aswitch operating coiland a switch holdin coil, the operating coils being energize successively with the acceleration of the motor to operate said switches successively, said holding coils being energized successively bv the operation of said operating C0115 to maintain a firm closure 'ofsaid switches, and means to decelerate the speed of the motor, comprising a decelerating control circuit, ada ted to energize'said operating coils successlvely in reverse order to that of the accelerating the operating coil of the next magnet in action and in opposition to the current passing through the holding coils to restore said magnets to normal position, and a switch operated by the return of each magnet to normal position to open the decelerating circuit through the operating coil of such magnet and close the decelerating circuit through order. 10 Signed by me at Boston, Massachusetts, this fourth day of April, 1912.

' l/v LLLIAM S. MITCHELL. Witnesses:

ROBERT CUSHMAN, CHARLES D. WOODBERRY.' 

